My experience so far seems to be opposite.
For some very odd reason. If I leave my native res at 4k in the game. DSR 4x and and go 60% on the render scale. I get choppy clouds. And shimmering on the cockpit window at night.
But by doing the opposite. FS at native 1080p and render sale at 140. Gives me solid 30fps at payware airports such as Zurich, dusseldorf. Clouds are smooth , no pixels on the clouds. Window shadows for the most part are smooth with very few dots . Overall it’s much improved picture quality than running everything at 1080p which I tried just to compare and my fps went down to 20-23fps with micro stutters.
I’ve also changed some more settings in the Nvidia control panel. Such as
Anisotropic filtering sample optimization OFF.
Negative LOD bias CLAMP
Continuing testing , I do short 1hr flights with live weather just make sure no CTDs happen. Unlike many people I’ve never had a CTD ever since I bought FS. I guess lucky me.